Hydraulic punch presses as shown in FIG. 1 are often used as fastener insertion machines. These presses include a C-type frame 8 and have upper and lower tools 3 and 6 held in vertical alignment which come together on opposite sides of a flat panel workpiece 5 to install a fastener into the workpiece under pressure. The upper tool is carried by a press ram 2 which extends and retracts vertically while the lower tool 6 remains stationary, being affixed to an anvil 9 mounted on the lower jaw of the frame 8 opposite the workpiece 5. The fasteners are typically delivered to the insertion site by escapement means 1 which holds each fastener against the end of the upper tool prior to insertion.
Individual tooling is specifically designed to install a particular type of fastener and since there are fasteners of different types and dimensions, separate tooling is required for installing each type. This therefore requires tooling changes when there is a change of fastener to be installed. It can become particularly problematic when one workpiece requires different types of fasteners. This requires either the tooling to be changed many times for each workpiece or for workpieces to be batched in lots and then re-run with a tooling change between each run. In either case, there are great inefficiencies and the increased opportunity for operator and/or workpiece handling errors.
In order to solve this problem, tool-changing devices have been created for fastener-installing punch presses such as disclosed in U.S. Pat. No. 6,106,446 issued to Kelly et al. and U.S. Pat. No. 6,135,933 issued to Kelly et al. These patents describe a tool-changing device in which a plurality of anvil tools may be interchanged by moving individual tools into and out of a tool clamp on the anvil. This requires rather complicated robotic handling of the individual tools which are delivered to the anvil site from a movable belt or other device that holds the individual tools in separate pockets below the anvil. When a tool is changed, the robotic device lifts the next tool out of a transfer pocket and into a clamp on the anvil to hold it in place. This system is very complex and expensive. More simplified anvil-mounted turret-type tool holders for punch presses are known, however they have no position-sensing means and cannot be used with monitoring controller software.
There is therefore a need in the art for a control system monitored tool-changing mechanism for a punch press which contains only a few components and which is rugged and reliable. Furthermore, there is a need for a rugged and reliable tool-changing system which is economical to manufacture and which provides position sensing means to ensure proper operation of the press.